It is also important to consider the thermalization of photoexcited carriers in our experiment. The QH edge is a one-dimensional Tomonaga-Luttinger liquid [1]} which, in an ideally clean system, lacks the thermalization processes that are present in Fermi liquids [2]}. Confirmation of this was provided by quantum-dot energy spectroscopy measurements identifying a nonequilibrium energy distribution as far away as 15 \(\mu \) m from the point of electrical excitation of the edge state [3]}. However, the QH edge in that work was defined by electrostatic gating, which creates a smooth confinement potential. It was shown that when electrons having several times the longitudinal optical (LO) phonon energy (36 meV) were injected into the QH edge, electrostatically broadening the edge potential suppressed scattering with these LO phonons, which hindered efficient equilibration [4]}. Further results indicated that relaxation by electron-electron scattering is also suppressed by edge potential broadening and increased excitation energy [5]}.
